Want to Pack On Muscle? Chill Out On HIIT.

You want bulging biceps and a bigger, broader chest. You want superheroic shoulders, and a ripped, chiseled back. What should your next move be? Get out of that high-intensity interval training class you keep attending. At the very least, you should stop making it the focus of your training.

I see it all the time. HIIT is fitness’ big buzzword at the moment, and, in my opinion, the second-most overused term in the biz. Too many people let the group fitness industry brainwash them into thinking that 40-seconds-on, 20-seconds-off of burpees, pushups, and squats will get them an action-hero body. It won't.

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HIIT has a place in any routine, and it's the perfect vacation go-to for a quick workout. Done correctly, the protocol has you doing bouts of quick work followed by short rest periods, which can leave your body dripping sweat and incinerating fat for hours afterward.The routines are also an excellent way to build a strong cardiovascular system, and in certain situations, enhance your explosive ability and athleticism.

But if you want Dwayne Johnson-level guns, drop the battle ropes and burpees and pick up some actual weights. Have you ever seen The Rock doing burpees? That's what I thought.

Why should you cool down on HIIT? To start, here are three key reasons:

1. More Load, More Gains

To build muscle, you need to progressively demand more from your muscles. That generally means you need to lift heavier weights throughout the course of a workout. HIIT doesn't place you in an ideal position to do that. The rest periods never fully let you recover so you can lift with clean form.

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What often happens: people who want to build muscle try going heavy in HIIT classes, but their form falls apart. Shoulder presses become push presses and jerks, and biceps curls become swings. All exercises become less about stressing a muscle and more about transferring momentum, because that's the mechanic that the body defaults to when fatigue sets in.

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HIIT may spark some initial muscle growth, but you'll eventually grow frustrated, because the gains will cease.

2. Failure to Focus

Most HIIT routines try to get around the fatigue on one muscle group by having you work multiple muscle groups in the same session. So instead of doing, say, 3 sets of traditional biceps curls followed 3 sets of a hammer curl to isolate one muscle, you'll do kettlebell swings and then immediately hit the deck for pushups, giving your hamstrings and glutes a chance to recover.

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Unfortunately, that type of rep structure robs you of the greatest qualities of traditional strength training protocols: The ability to focus on one or two muscle groups per session.

HIIT doesn't offer enough recovery time to do that, so you never build a strong mind-muscle connection. You're constantly training a different body part, so you never get fluid in any exercise. You'll never get to feel what bodybuilders refer to as "the pump," when blood rushes to a targeted and isolated muscle to bring nourishing, muscle-building nutrients.

3. High Frequency, High Failure

HIIT isn't something you can do every day (unless you're Odell Beckham-fit). Most training professionals — the good ones, at least — will only put you through a full HIIT workout twice a week, so that your body has time to recover. Do HIIT too often and here's the result: your intensity drops off from workout to workout, and by the third straight day, you're not able to go as hard.

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Moderate-intensity programs don't have that problem. Yes, you need to recover — but in a protocol in which you're training different body parts each day, recovery happens organically. You slam chest one day, then your pecs get to "rest" as you home in on legs and biceps on the next two days.

THE NEW HIIT PLAN

If you're serious about building muscle, you can keep HIIT in your routine — but not the way it's done on the group fitness circuit. Instead, start trying body part-specific workouts (you can find plenty of them right here), so you can really pack on the size you want.

You can end each workout with 10 to 15 minutes of HIIT work, since this will ratchet up your heart rate and get your body moving, building your cardiovascular system and frying fat. Or do a full-length HIIT workout once or twice a week, using the session to supplement your muscle-growing strength program.

That way, you get the best of both worlds. You're still able to get in on those trendy fitness classes — but your superhero-sized muscles will continue to build up, making your hard work worth the while.

Ebenezer Samuel, C.S.C.S.Ebenzer Samuel, C.S.C.S., is the fitness director of Men's Health and a certified trainer with more than 10 years of training experience.

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